The well known Japanese infantry weapons which was the type 38 arisaka rifle and the type 3 heavy machine gun seemed to be better suited for Ww1 or interwar years combat when compared to the Semi automatic rifles and ubiquitous american weaponry.
I had also heard that the regular japanese infantry man did not have a submachine gun as part of his primary weaponry, The most common japanese submachine gun, the type 100, only had 27k units made and was regulated to special units.
So my question is why were japanese infantry weapons in Ww2 seemingly inferior to their allied counterparts considering that japan had an emphasis on their army?
Was it for example due to their military doctrine and how they conduct warfare or lack of production capabilities?
On a side note Japan seemed to also lack adequate Armored vehicles when compared to American Shermans and stuarts, although Japanese tanks proved useful in china.
I don't think they were inferior as opposed to how expensive it is to retrofit an army with newer weapons.
We have to realize that on a resource scale, America's industrial capacity in of itself is larger by magnitudes compared to Japan. Likewise, we also have to remember that even the M1 Garand wasn't entirely used into service (many of the 1903s were still used well into 1944) due to how expensive it is to deploy and retrain soldiers with new weapons.
With this in mind we also have to remember that Japan had been fighting even before WWII broke out. Deploying newer weapons across the battlefield would have taken quite a long time. For comparison, look at the majority of Germany's Kar98k usage and Russia's Mosin Nagant usage. Most troops still used bolt action rifles well into the end of the war. Not only due to supply issues, but also because of cost of fitting out an entire unit with new weapons.
For even further reference, look at the G.43 and SVT 40 usage rates during WWII.
I'd wager that Japan just didn't have the capacity to produce large battalions of armored vehicles thanks to the relative lack of materials and the lack of fuel. Even in aviation the production quality suffered rather badly near the end of the war. So I'd nail it down to less that the Japanese were inept as much as they were genuinely limited in resources and development capacity due to being embroiled in conflict.
Theres often not a specific reason for these things. As in, no one sat in a meeting and said 'Semi-auto assault rifles, nope, we dont need those'. It is more, as you suggest, a result of doctrine and practice. The Japanese infantry was enormously efficient for the terrain they were fighting in. Either jungles/heavily forested terrains of SE Asia or various Pacific islands. Nor were Japanese defeats based on the inferiority of their infantry weapons as such. Tough physical environments with high humidity, long supply lines and heavy going terrain quite often favour simpler weapons.
Later on as the American assault in the pacific gathered pace the weight of firepower increased and the Japanese lacked the ability to keep up with that firepower. But the die was cast for their defeat primarily due to the preponderance of Air and Sea power the allies had later on. Heavy Japanese tanks , built Tiger-style, would have made little difference at places like Io Jima and would have been knocked out quickly, more hindrance than help.
The Japanese often suffered issues with supply lines. Too many tanks, machine guns and artillery would have only made that worse.
Industrial capacity may have also affected this as well.
In places like Burma both sides were generally lightly armed, with little use of artillery and tanks of any sort.
So European battles 'created' European armies, Asian battles created Asian armies. The US were probably, when counterattacking, a 'heavier' force than their japanese counterparts, but this was a function of their assault on dug-in-forces.
When Australian forces fought the Japanese in New Guinea on the famous Kokoda trail the 2 forces were largely matched weapons-wise, with the eventually triumphant Aussies having a degree of advantage in the long run by being the 'home' side and have better supply logistics.
So in essence I dont feel that the Japanese stuff was innately inferior, I think it suited the simpler and tougher environment of their military involvements.
Another factor may be that the Japanese had been involved in some sort of war for most of the previous 10 years and may have been more in a 'resupply of existing equipment' mode than an innovate and reinvent one. And 10years of reasonably succesful activity doesnt spur a great urge to change.